Spreading are: plug-in hybrid electric vehicles (PHEVs) employing an electric motor and a combustion engine in combination; and electric vehicles (EVs) driven by an electric motor without employing a combustion engine. A vehicle such as a plug-in hybrid electric vehicle and an electric vehicle includes a battery driving the electric motor. Then, charging of the battery is performed by using an external power supply apparatus installed in an electricity supply station, an ordinary house, or the like.
FIG. 10 is a block diagram illustrating the configuration of a vehicle connected to a power supply apparatus. A power supply apparatus 2 includes a charging cable 3 whose end is provided with a charging gun to be connected to a vehicle 1001. The vehicle 1001 includes a connector 11 to which the charging gun is to be connected. Thus, with a user connects the charging gun to the connector 11, the power supply apparatus 2 is allowed to be connected to the vehicle 1001. The charging cable 3 includes: two power feed lines 1001a and 1001b; a reference potential line 1001c; a control line 1001d; and a connection detection line (not illustrated) detecting the connection of the charging gun. The power feed lines 1001a and 1001b are connected to a charging device 12 mounted on the vehicle 1001. The reference potential line 1001c is connected through the charging device 12 to the reference potential. For example, the reference potential is a body ground of the vehicle 1001. The power supply apparatus 2 supplies an alternating current through the power feed lines 1001a and 1001b to the charging device 12. Then, the charging device 12 converts the supplied alternating current into a direct current and then performs charging of the battery 10. The control line 1001d is connected through a PLC communication device 1014 to a CP receiving circuit 1013. The CP receiving circuit 1013 is a circuit receiving a control pilot signal transmitted from the power supply apparatus 2. Then, in accordance with the transmission and reception of the control pilot signal, the power supply apparatus 2 performs charging control (e.g., SURFACE VEHICLE RECOMMENDED PRACTICE”, J1772 February2012, Society of Automotive Engineers, Inc., October 1996 (Revised version, February 2012)). The control pilot signal is a signal of rectangular wave form. Then, in accordance with the potential of the rectangular wave signal relative to the reference potential, the presence or absence of the rectangular wave signal, and the like, the power supply apparatus 2 transmits and receives information concerning the charging such as the permission or non-permission of charging and the charging status.
Further, the PLC communication device 1014 connected individually to the control line 1001d and the reference potential line 1001c is mounted on the vehicle 1001. The PLC communication device 1014 superposes a differential signal having a higher frequency than the control pilot signal, for example, a differential signal of 2 to 30 MHz, onto the control pilot signal or, alternatively, separates a differential signal superposed on the control pilot signal so as to perform communication employing a differential signal. The power supply apparatus 2 transmits and receives the differential signal to and from the PLC communication device 1014 so as to be allowed to perform more advanced information communication than that performed by employing the control pilot signal.
As described above, the PLC communication device 1014 transmits and receives the differential signal through the control line 1001d and the reference potential line 1001c. The control line 1001d is connected to the PLC communication device 1014 having a given impedance. However, the reference potential line 1001c is connected to a body ground having a low impedance. Thus, in this configuration, the balance of the PLC communication device 1014 is unsatisfactory. Accordingly, a common mode noise generated in the control line 1001d and the reference potential line 1001c through the body ground or the like is converted into a noise of differential mode and then inputted to the PLC communication device 1014 as illustrated in FIG. 10. The PLC communication device 1014 performs communication by using a differential signal of 2 to 30 MHz. Thus, a noise of differential mode of 2 to 30 MHz is not allowed to be separated and removed. This has caused a problem of malfunctioning of the PLC communication device 1014.
Here, a method may be employed that a common-mode choke coil is provided in the control line 1001d and the reference potential line 1001c so that the malfunctioning of the PLC communication device 1014 is avoided. However, in some cases, the noise generated in the control line 1001d and the reference potential line 1001c is not allowed to be effectively removed. This is expected to be because a part of the common mode noise generated in the control line 1001d and the reference potential line 1001c is not removed by the common-mode choke coil and is converted into a noise of differential mode so as to be inputted to the PLC communication device 1014.